Field of the Invention
The present invention relates to an electronic apparatus and a shock detection method.
Description of the Related Art
Conventionally, there have been available electronic apparatuses configured to generate an alarm sound when a predetermined time is attained in time measurement. One of such electronic apparatuses is equipped with a mechanism allowing the user to stop the alarm sound generated by imparting a shock to the electronic apparatus.
For example, JP-A-63-79091 discloses an alarm electronic timepiece having a first piezoelectric element firmly attached to a part of a timepiece case member for generating an alarm sound, a second piezoelectric element for detecting a shock applied to a timepiece case, a detection circuit configured to detect a voltage signal generated by the second piezoelectric element, a level discrimination circuit configured to output solely an output signal of not less than a fixed level of output signals of the detection circuit, and a timepiece circuit for performing time measurement or the like. The electronic timepiece is equipped with a switch device for the electronic timepiece which, even when an alarm signal for generating an alarm sound is being applied to the first piezoelectric element due to the timepiece circuit, operates the detection circuit and the timepiece circuit by the voltage signal of the second piezoelectric element generated by an impact force applied to the timepiece case.
Further, the switch device of the electronic timepiece disclosed in JP-A-63-79091 is formed as follows: for the first piezoelectric element and the second piezoelectric element, there is provided a common electrode extending over substantially the entire area of a first surface of the same piezoelectric material; two independent electrodes are provided on a second surface thereof; the first surface is press-fitted to the timepiece case; one electrode provided on the second surface is formed as the electrode of the first piezoelectric element; and the other electrode is formed as the electrode of the second piezoelectric element.
However, the switch device for the electronic timepiece disclosed in JP-A-63-79091 is equipped with a second piezoelectric element for detecting a shock independently of the first piezoelectric element for generating an alarm sound, resulting in an increase in the number of components. To achieve a reduction in the apparatus size, a piezoelectric element of a small size is used as each piezoelectric element, whereby the maximum volume of the alarm sound that can be generated is reduced, and the signal value of the shock detected is reduced, so that the detection of the shock is rather difficult. Further, when a common electrode for the first piezoelectric element and the second piezoelectric element is provided so as to extend over substantially the entire area of a first surface of the same piezoelectric material, a step-up coil may be connected in parallel with the first piezoelectric element in order to apply a large voltage to the first piezoelectric element for generating an alarm sound. The step-up coil exhibits high impedance with respect to a high frequency signal, and low impedance with respect to a low frequency signal. Thus, with respect to a signal corresponding to a shock of lower frequency than the alarm sound, it is substantially brought into conduction, so that it is difficult to detect such a shock.